The K. Marxianus Small Protein Modifier Sumo Enhances Stress Tolerance In The Mesophilic Yeast S. Cerevisiae

SUMO, a small ubiquitin-like modifier protein, becomes attached to specific eukaryotic proteins to modulate their function and activity. The importance of SUMO modification in cell cycle progression, transcriptional regulation, and DNA damage-related processes has been firmly established. In contrast, a SUMO-dependent Stress Response (SSR) exists, but this process remains ill-defined. When cells are exposed to proteotoxic and genotoxic stressors, the SSR involves a rapid and dramatic increase in SUMO-modified proteins. The SSR is believed to play a cytoprotective role for normal cells, but it may also enhance the robustness of cancerous cells and eukaryotic pathogens. To test our hypothesis that SUMO and SUMO pathway components play a role in stress tolerance, we utilize the stress tolerant yeast Kluyveromyces marxianus (Km). Unlike Saccharomyces cerevisiae (Sc) cells, Km cells thrive at temperatures of up to 49°C and are highly resistant to oxidative stress and UV irradiation. By utilizing Km, we aimed to I) establish whether sumoylation and the SSR play a role in stress tolerance of Km and II) identify specific SUMO pathway components involved in stress tolerance of Km. Our results reveal that Km displays a distinct SSR. Additionally, by cloning nine Km SUMO pathway genes and using CRISPR/Cas9 technology, we were able to replace Sc SUMO with its Km ortholog and found that this replacement enhances the resistance of Sc cells to oxidative stress